1. Field of the Invention
This invention relates in general to multiline key telephone instruments having line select pushbuttons switches and more particularly to a mechanism for automatically restoring an operated pushbutton.
2. Description of the Prior Art
It has become common in modern telephone systems to provide subscribers's telephone sets with means of enabling them to perform certain switching operations apart from those which usually result from removal or replacement of the telephone instrument handset with respect to the hookswitch or cradle. For instances, a plurality of pushbutton keys which enable a telephone subscriber to select any one of several telephone lines to converse with others.
Normally selection of a particular line is accomplished by activating or depressing a pushbutton into an activated position to enable that particular line to either answer a call or to place a call. A special or reset pushbutton may be provided which when depressed releases any depressed pushbutton. In prior art systems, when the subscriber has completed a particular phone call he pushed a reset button in order to cut-off his telephone receiver from a partciular telephone line, thus enabling others to use the circuit without interference. The reset button technique suffered from the obvious deficiency that people would often forget to push the reset button. This resulted in interference with subsequent users of that particular line.
Thus, it becomes advantageous to provide a mechanism for automatically restoring a depressed line selection pushbutton after a call has been completed. Such mechanisms for automatic button restoral are taught by U.S. Pat. No. 2,780,677 to L. Schaufuss, issued on Feb. 5, 1957, 3,601,559 to E. S. Hineline, Jr., issued Aug. 24, 1971 and 3,903,070 to I. Kunimine, issued Sept. 2, 1975. Such systems have been overly complicated from a mechanical standpoint making them costly to manufacturer and install and, required many critical adjustments to operate dependably.
Therefore, it is an object of the present invention to provide a simple, effective, pushbutton restoral mechanism for restoring a depressed line key pushbutton by replacing the telephone instruments handset on the telephone cradle.